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M- 11 F June 29, 1988 tY AGS Job No. 86102-3 Page 2 the ground-water surface between the three wells is less than the instrument error (0.02 feet over the required distance) . The potentiometric surface is, therefore, inferred to be essentially flat. Samples of ground water from the air-fluid interface were collected after initial water levels measurements in the monitoring wells. These samples were collected for subjective analyses by lowering a 7aflon bailer approximately halfway through the interface. The bailer was then retrieved, and the water sample was examined for floating product, sheen, and other subjective evidence of hydrocarbon contamination. No floating w product, product sheen, or emulsionwas noted in samples from the monitoring wells. Product..odor was detected in well MW-1. Cumulative resultsof these a Presented in Table 1, ,�d Previous subjective analyses are Ground-water monitoring wells MW-1, 14W-2, and MW-3 were prior to sampling, using an electric submersible purged a PSP• One- , hundred gallons of ;watex.were" removed from each well. After the ? � ground-eater was allowed to recover to static level, samples were collected by lowering a clean Teflon bailer through the air- water interface to a point approximately 10 feet below the interface. The water was then transferred to laboratory-cleaned 40-milliliter glass volatile organic analysis vials. Concentrated hydrochloric acid was added as a preservative. A Chain of Custody Record was initiated in the field by the sampler and accompanied the samples to Applied GeoSystems' analytical laboratory in Fremont, California. A copy of this record is attached.. ;t The samples were analyzed for total petroleum hydrocarbons by Ehvironmental. Protection Agency (EPA) Method 8015 (modified for gasoline) , and for the volatile hydrocarbon constituents benzene, ethylbenzene, toluene, and total xylene isomers (BETX) by EPA Method 602. Applied GeoSystems' laboratory is certified by the state of California for these analyses. Copies of the. laborator Records of Analyses are attached. y The results of the analyses, summarized in Table 2, indicate that the levels of benzene in ground water taken from the monitoring wells exceed the._maximum._levels--far drinking — - - - ------'-- the DHS. The levels of other volatile constituents are below the. s maximum levels recommended by the DHS. The concentrations of all volatile hydrocarbon constituents (BETX) in ground-water from wells MW-1 and MW-2 have decreased since the last analyses; ground-water in well MW-3 contains slightly higher concentrations of these constituents than found in the previous analysis. i AORIlsd Geosystwns